Lubrication of respective sliding portions of a compressor used for a refrigerator is ensured by a lubricating oil having a good miscibility with a refrigerant contained in a cooling medium returned thereto. However, upon starting operation of the compressor, a certain period of time is required until the returned refrigerant in the compressor is fully supplied to the respective sliding portions, thereby causing such a problem that defective lubrication may occur at the sliding portions upon the starting. In order to compensate the defective lubrication upon starting operation of the compressor, there has been proposed the method of coating these sliding portions with a lubrication film-forming composition containing a solid lubricant (for example, refer to JP 7-247493A).
However, only such a coating lubrication film formed on a surface of the respective sliding portions fails to impart a fully satisfactory lubrication performance thereto upon the starting. Under some conditions, the coating lubrication film tends to suffer from abrasion, resulting in occurrence of seizing at the sliding portions.
Also, even under a steady operational condition of the compressor, a bearing surface pressure of the respective sliding portions thereof tends to be unsuitably increased depending upon kind of refrigerant used, for example, when using a carbon dioxide refrigerant, etc. As a result, even if the coating lubrication film is formed on the sliding portions, the coating layer tends to suffer from abrasion owing to the increased bearing surface pressure, thereby causing defective lubrication of the sliding portions.